The invention relates to a holding device for rod-shaped components, particularly a Christmas tree stand.
Holding devices of this type are known to exist in various designs.
One example of this is the tree stand according to the patent specification DE 102 20 879 A1 of the applicant. In this tree stand, the holding elements are designed as pivoted levers, which are linked to the receiving part of the tree stand and whose end side comprises a contacting region, by means of which every holding element comes into contact with the tree trunk during the tensioning process of the tensioning device. A flexible connecting element—usually a rope—which can be subjected to a tensile load or be loaded in tension and which is guided such that it can move transversely to the holding elements and engages at the latter, is used for this purpose.
It has also already been proposed (DE 100 00 879 A1; DE 200 23 309 U1; EP 1 318 740 B1; DE 299 04 435 U1; DE 299 13 474 U1), to use several flexible connecting elements, instead of one—specially a rope—and to assign them to each holding element or to each group of holding elements.
In these cases, the pivoted levers extend upwards from their points of articulation on the foot part or on the receiving part of the tree stand in such a way that each of them can be pivoted in a plane between their releasing position and their holding position, said planes intersecting approximately in the axis of symmetry of the stand. Each contacting region is designed on the upper end of the pivoted lever on its side facing the axis of symmetry, said upper end being opposite to the point of articulation.
However, it has also been proposed (DE 195 45 471 A1; DE 196 32 305 A1), to use levers in horizontal alignment instead of such upwardly extending pivoted levers or even axially moving bolts (DE 100 00 879 A1), which are guided aligned to the center of the tree stand, or pushing elements (German Utility Model no. 20 2004 020 005 8) instead of pivoted levers.
In all these tree stands, it is possible to distinguish several operating states from one another: In the releasing position the holding elements release the receiving part for inserting or taking out the rod-shaped component, e.g., a tree trunk—i.e., the holding elements are not yet in contact with the tree trunk. When the tensioning device is actuated, this releasing position is followed by the contacting position in which the holding elements contact the tree trunk. Thus in this position, it is still possible, for example, to align the tree, however without the tree being held conveniently, as a result of which the alignment can be lost easily before the tree can be finally clamped firmly. When the tensioning device is slightly actuated further, the contacting position is followed directly by the holding position. In the holding position, the holding elements rest against the tree trunk with a considerable holding force. The tree is thus clamped firmly and thus can also hardly be aligned. As a result it is hardly possible to correct alignment errors. There is an even lesser likelihood of correcting alignment errors if the holding elements, as mostly known from prior art, bear one or more sharp peaks, claws or the like, which dig into the tree trunk during the tensioning process immediately after the contacting position is exceeded, in order to hold the tree trunk particularly tightly.
In order to ensure that the tree trunk can be aligned easily and reliably before being finally fixed into place and without losing this alignment before the holding position is reached, the applicant (Utility Model no. 20 2004 020 005 8) has proposed to design the contacting regions of the holding elements as arched, smooth sliding surfaces, for example, convexly or cylindrically instead of with peaks, claws or the like, and thus to create an additional defined aligning position as an intermediate position between the contacting position and the holding position. In this position, the holding elements already hold the tree trunk with a certain contact pressure. Thus, for example, the tree trunk would not topple down easily if it were released. However, the tree trunk can slide on the contacting regions for the purpose of the alignment. Furthermore, in said Utility Model Specification, the applicant has already proposed to design the contacting regions elastically for further facilitating the alignment. Once the desired position of the tree trunk is reached, the holding elements can then be transferred out of the aligning position into the final holding position by actuating the tensioning device over a very slight tension path. Using the conventional tensioning devices of the type of a ratchet, this final tensioning can take place e.g., in an uninterrupted process.
For the same purpose the applicant has additionally proposed in the German Utility Model no. 20 2004 020 006 6 to create a defined aligning position by designing the holding elements themselves to be resilient or by assigning to each holding element an elastic buffer element in its contacting region. During the tensioning process, said buffer region is pressed against the tree trunk with a defined, adjustable force that is smaller than the force applied in the holding position and that is applied such that the tree trunk is fixed temporarily, however is not yet alignable. As a result, the holding elements can deploy their full holding force only when the buffer action of the elastic element is used up. The applicant has further proposed to assign the elastic buffer element for the same purpose to the flexible connecting element, which can be subjected to a tensile load or be loaded in tension.
Particularly the proposals of the applicant to create a separate aligning position by the slidable smooth configuration of the contacting regions or by incorporating a buffer have yielded good practical results. They have eliminated the difficulties when aligning the tree trunk, said difficulties being caused by the pointed or claw-shaped contacting regions known from prior art. However, these proposals also exhibit certain shortcomings. The installation of buffer elements is structurally relatively cumbersome and prone to breakdown in certain circumstances. Indeed the slidable smooth design of the contacting regions improves the behavior of the holding device when aligning the rod-shaped component. However, due to the absence of an appreciable slide-resistance, relatively large holding forces are required in the holding position if the tree trunk is to be supported in a really secure manner. This calls for a relatively robust construction, which is expensive in terms of material and costs if damages caused by premature fatigue of material are to be avoided.
Incidentally, what is common to all the solutions proposed in the prior art is that the contacting regions are designed uniformly in the respective selected configuration—regardless of whether they are provided with sharp peaks or are designed to be smooth or rounded and smooth, or even cylindrical or provided with a buffer element. That is, the contacting regions comprise either one or more claws or peaks with all their above-mentioned advantages and disadvantages (good holding force, poor possibility of alignment) or a smooth, arched surface, if appropriate, which indeed facilitates the alignment, however requires considerable pressing forces for holding the tree trunk securely. In the solutions with a buffer element also, a homogeneous contacting region is always provided, which is not adapted to the different operating states. The additional structural measures such as buffer elements, elastic design of the components, single rope technique or multiple rope technique could indeed reduce, though not dispel the disadvantages of the respective homogeneous configuration of the contacting regions.